THROMBOSIS RISK IN ESSENTIAL THROMBOCYTOSIS CORRELATES WITH HEMOGLOBIN VALUES Study group for acute leukemias and myeloproliferative neoplasms Greek Society of Hematology Greek Society of Hematology This study derives from a multicentre registry of greek patients with essential thrombocytosis, held by the study group for acute leukemias and myeloproliferative neoplasms of the Greek Society of Hematology. The registry contains so far 548 patients, 42% of whom are male. In 79% of them an elevated platelet count was an accidental finding. Thromboembolic and hemorrhagic events were observed in 16.4% and 5.5% of them respectively before the onset of treatment. In 20.2% there was a preexisting cardiovascular condition, for instance coronary disease in 13.5%. In 2.9% family history of cardiovascular disease was reported. (Table 1) Patients548 Male42% Female58% Accidental finding79% Hemorrhagic event5.5 % Thromboembolic event16.4% Preexisting cardiovascular disease20.2% Family history of cardiovascular disease 2.9% JAK-2 positive patients tend to be older (64 vs 56 years old, p=0.0002) and to have higher hemoglobin values than the rest (14.08 vs 13.32, p=0.0001).JAK-2 positive patients tend to be older (64 vs 56 years old, p=0.0002) and to have higher hemoglobin values than the rest (14.08 vs 13.32, p=0.0001). No correlation was observed between JAK-2 mutation presence and fibrosis, splenomegaly, white blood cell or platelet count.No correlation was observed between JAK-2 mutation presence and fibrosis, splenomegaly, white blood cell or platelet count. Thrombosis also correlates with hemoglobin values (13.6 vs 19.3, p=0.086) but not with white blood cell or platelet count.Thrombosis also correlates with hemoglobin values (13.6 vs 19.3, p=0.086) but not with white blood cell or platelet count. Hudroxyurea was the treatment best tolerated and exhibited the best response rates in comparison to anagrelide and interferon (93.2.% vs 73.9% and 80.6%).Hudroxyurea was the treatment best tolerated and exhibited the best response rates in comparison to anagrelide and interferon (93.2.% vs 73.9% and 80.6%). Results JAK-2 mutational status was checked in 64.2% of the patients but misses in the rest, depending on the year of diagnosis (mean year of diagnosis 2005 vs 2001, p<0.0001). In 55.1% the V617F mutation was detected. (Graph 1) In 70% of the patients no fibrosis in trephine biopsy was detected, whereas fibrosis grade I or II was found in 21%, and 9% respectively. (Graph 2) In 37% of the patients a watchful waiting strategy for more then 6 months was adopted, whereas hydroxyurea, anagrelide and interferon were first-line therapies in 52%, 7% and 4% respectively. (Graph 3) In 37% of the patients a watchful waiting strategy for more then 6 months was adopted, whereas hydroxyurea, anagrelide and interferon were first-line therapies in 52%, 7% and 4% respectively. (Graph 3) Thrombosis or hemorrhage during therapy was observed in 6.2% and 3.1% respectively. Secondary malignancies concerned 5.5% of the patients, 2.2% of them being hematologic. Table 1: patient characteristics concerning age, diagnosis symptoms and history Graph 1: JAK-2 mutational status JAK-2 (+) JAK-2 (-) Graph 2: bone marrow fibrosis percentages (white: no fibrosis, black: grade I, grey: grade II) Graph 3: initial therapy (white: watchful waiting, black: hydroxyurea, grey: anagrelide, dotted: interferon) D. Sotiropoulos, T. Marinakis, P. Tsirigotis, M. Iskas, V. Papadopoulos, E. Papadakis, E. Spanoudakis, I. Kotsianidis, A. Pouli, A. Vassou, A. Pigaditou, A. Balta, M. Dimou, M. Kotsopoulou, C Matsouka, M. Protopapa, E. Vlachaki, I. Koratzis, I. Dervenoulas, N. Anagnostopoulos, P. Panayotidis, A. Anagnostopoulos